Model rocket motor retainer apparatus

ABSTRACT

A model rocket motor retainer apparatus for model rockets comprised of two components, a cylindrical retainer body ( 1 ) and an aft closure ring ( 2 ); wherein the retainer body is attached to a rocket motor tube ( 3 ), and the aft closure ring attaches into the aft end of the retainer body ( 3 ). Installation and tightening of the aft closure ring traps the rocket motor ( 4 ) between the aft closure ring and the rocket motor tube, thereby positively retaining the motor.

BACKGROUND

[0001] 1. Field of Invention

[0002] This invention relates generally to model rockets, specificallyto such devices used for retaining a rocket motor within a rocketairframe.

[0003] 2. Description of Prior Art

[0004] One of the many challenges in the recreational hobby of modelrocketry is the ability to retain the motor(s) during the recoverydeployment phase of flight. Sometime after the boost phase of a modelrocket flight the typical rocket relies on an ejection charge, firing inthe forward direction, to deploy the recovery system thus insuring asoft landing. Most model rocket motor manufacturers build such ejectioncharges into their motors. In the event the motor is not adequatelyretained in the rocket airframe during the firing of the ejectioncharge, two undesirable actions may occur. First, the recovery systemmay not deploy due to lack of inner cavity pressure thus causing therocket to crash dangerously to the earth. Second, motor casings might beejected in the aft direction and possibly lost.

PRIOR ART

[0005] Existing motor retention designs include “motor hooks”, bolt-on“bracket” style retainers, “screw-on cap” style retainers, and“retaining ring” style retainers.

[0006] “Motor hook” style retainers, as disclosed in U.S. Pat. Nos.5,267,885 and 5,212,946, are basically a bent strip of metal,permanently attached to the motor tube, that extend over the rear of therocket motor, thereby securing the motor.

[0007] Bolt-on “bracket” style retainers, such as described in U.S. Pat.Nos. 6,155,173, are a U-shaped or Z-shaped bent metal strip that boltsto the rear bulkhead of a rocket airframe, with a flange that extendsover the rear of the rocket motor, thereby securing the motor.

[0008] “Screw-on cap” style retainers are comprised of an externallythreaded cylindrical retainer body glued to the outside of the motortube, and a mating external cap of a larger diameter than the retainerbody, which screws onto the cylindrical retainer, thereby securing themotor.

[0009] “Retaining ring” style retainers are comprised of a cylindricalretainer body glued to the outside of the motor tube; the retainer bodyhas a retaining ring groove machined on its inside diameter near the aftend, which mates with a commercially available retaining ring to trapthe motor between the retaining ring and the motor tube.

OBJECTS AND ADVANTAGES

[0010] Accordingly, objects and advantages of the present inventioninclude:

[0011] Provision of a method of motor retention of sufficient strength,yet which minimizes frontal area and thus aerodynamic drag for optimummodel rocket stability and performance. Prior art, such as externalscrew-on cap type retainers, have a cap outside diameter significantlylarger than the retainer body; use of these type retainers on minimaldiameter rockets increases aerodynamic drag and thereby reduces rocketstability and performance.

[0012] Provision of a method of motor retention that accommodates motorswith rear thrust rings of varying lengths. Prior art, including screw-oncap type retainers, bolt-on bracket style retainers, and retaining ringstyle retainers, once installed, accommodate only one rear thrust ringlength. The present invention allows the rear closure to be screwed intothe retainer body as required to trap rear thrust rings of less thannominal length, thereby providing adjustability and flexibility ascompared to previous designs.

[0013] Provision of a method of motor retention that accommodates motorsequipped with or without rear thrust rings. Existing retainer designs,such as retaining ring style motor retainers, are better suited tomotors with rear thrust rings. When retaining ring style retainers areused with motors that do not have rear thrust rings, the smallerdiameter of the recoiling motor bears against the inner diameter of theretaining ring, rather than against the full exposed diameter, therebyloading the retaining ring improperly and increasing the potential forfailure.

[0014] Further objects and advantages will become apparent from aconsideration of the ensuing description and drawings.

SUMMARY, RAMIFICATIONS, AND SCOPE

[0015] In accordance with the present invention, a model rocket motorretainer apparatus comprises a cylindrical retainer body and an aftclosure ring adaptable for various rocket motors.

[0016] Thus the reader will see that the rocket motor retainer of thepresent invention provides a highly reliable, economical, lightweightyet easy to operate device, components of which can be usedinterchangeably on many rocket kits by a model rocketry enthusiast.

[0017] While the above description contains specificity, thisspecificity must not be construed as limitations on the scope of theinvention, but rather as an exemplification of one preferred embodimentthereof. Many variations are possible. For example, the describedcomponents of the invention can be made smaller or larger; they can beincorporated into related devices such as motor adapters or retainertail cones, or can have various design accommodations made on the mountfor other methods of attachment to the rocket frame.

[0018] Accordingly, the scope of the invention should be determined notby the embodiment(s) illustrated, but by the appended claims and theirlegal equivalents.

DESCRIPTION OF DRAWINGS

[0019] Reference Numerals in Drawings

[0020]1 retainer body

[0021]2 aft closure ring

[0022]3 rocket motor tube

[0023]4 rocket motor (with integral thrust ring)

[0024]5 rocket motor nozzle

[0025]6 rocket fin

[0026]7 rocket airframe tube

[0027]8 retainer body (as tail cone)

[0028]9 rocket motor (without integral thrust ring)

[0029]10 retainer body (as adapter)

[0030]11 through bore

BRIEF DESCRIPTION OF THE DRAWINGS

[0031]FIG. 1 shows the isometric aspect of a model rocket motor retainerapparatus.

[0032]FIG. 2 shows an isometric exploded view of the retainerinstallation on a minimum diameter rocket application.

[0033]FIG. 3 shows a sectional view of an operational demonstration of amodel rocket motor retainer apparatus in a typical minimum diameterrocket application.

[0034]FIG. 4 shows a sectional view of an operational demonstration of amodel rocket motor retainer apparatus in a typical non-minimum diameterrocket application. In addition, this view demonstrates the tail conevariant of the retainer body, as well as the retention capability forrocket motors without an integral rear thrust ring.

[0035]FIG. 5 shows a sectional view of an operational demonstration of amodel rocket motor retainer apparatus in a typical non-minimum diameterrocket application in which the inner retainer body demonstrated theadapter variant.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0036] A typical view of the model rocket motor retainer is illustratedin FIG. 1 (isometric view), while an exploded view of the assembly ofthe retainer apparatus on a typical minimum diameter rocket is shown inFIG. 2. The retainer apparatus has a cylindrical retainer body (1) thatmay be adhesively or mechanically attached to the rocket's motor tube(3) and becomes a permanent component thereof. The aft end of theretainer body is internally threaded. The aft closure ring (2) isexternally threaded and screws into the mating threads on the retainerbody aft inner diameter.

[0037] Operation—FIGS. 3, 4, & 5

[0038] Motors with Integral Thrust Ring—FIG. 3:

[0039] Once the motor (4) has been inserted into the motor tube (3) suchthat the motor aft thrust ring abuts the aft end of the motor tube (3),the threaded aft closure ring (2) is screwed into the aft end of thecylindrical retainer body (1) and tightened as required to contain themotor.

[0040] Motors without Integral Thrust Ring—FIG. 4:

[0041] Once the motor (9) has been inserted into the motor tube (3) suchthat the motor forward end abuts the thrust bulkhead integral to themotor tube (3), the threaded aft closure ring (2) is screwed into theaft end of the cylindrical retainer body (1) and tightened as requiredto contain the motor.

[0042]FIG. 4 also shows a retainer body variant (8) in which the outercontour aerodynamically transitions from the motor tube diameter (3) tothe airframe tube diameter (7) for use on rockets with an airframe tubeof larger diameter than the motor tube.

[0043] Adapter Retainer Body Variant—FIG. 4:

[0044]FIG. 4 shows a retainer body variant (10) in which the outercontour of the retainer body simulates a larger model rocket motor withthrust ring. This adapter variant, which allows for use in installingsmaller motors in larger motor tubes on retainer-equipped rockets, canbe retained within the rocket airframe tube by a normal retainer body(1) and rear closure (2) as if it were a rocket motor.

I claim:
 1. A model rocket motor retainer apparatus comprising aretainer body and an aft closure ring attached to said retainer body, asa means for retaining a model rocket motor within a rocket airframe. 2.A model rocket motor retainer apparatus per claim 1 wherein said aftclosure ring further includes appropriately sized through-bores as ameans to accommodate rocket model motors of various sizes.
 3. A modelrocket motor retainer apparatus per claim 1 wherein said retainer bodyfurther includes a minimal outside diameter as a means to provideimproved aerodynamic characteristics through drag reduction.
 4. A modelrocket motor retainer apparatus per claim 1 wherein said retainer bodyfurther includes internal threading on the aft inside diameter as ameans to accommodate rocket motors with rear thrust rings of varyinglengths.
 5. A model rocket motor retainer apparatus per claim 1 whereinsaid retainer body further includes an outer conical, ogive, or similarcontour, that aerodynamically transitions from a rocket motor tubediameter to an airframe tube diameter for use on rockets with anairframe tube of larger diameter than the motor tube.
 6. A model rocketmotor retainer apparatus per claim 1 wherein said retainer body furtherincludes an outer contour shaped to simulate a larger model rocket motorwith a thrust ring as a means for adapting smaller rocket motors forinstallation in larger motor tubes.